Interoperability and integration of the Long Term Evolution (LTE) system of 3GPP and the Wireless Local Area Network (WLAN) at the core network level have been defined in the 3GPP standardization documents. 3GPP LTE Release 12 has studied the interoperability and integration of LTE and WLAN at the RAN level (see 3GPP TR37.834).
At the 3GPP TSG RAN #67 meeting, a research proposal was approved to enhance the integration and interoperability of LTE-WLAN at the RAN level in 3GPP LTE Release 13 (see 3GPP Proposal RP-150510). Research on enhancing integration and interoperability of LTE-WLAN at the RAN level includes: enhancing integration of LTE-WLAN at the RAN level and enhancing the interoperability of LTE-WLAN at the RAN level. The integration of LTE-WLAN at the RAN level means that user equipment in the RRC connection state is configured to utilize the radio resources, provided by both LTE and WLAN, at the same time, all the while not affecting the existing standards on the MAC layer of WLAN. Enhancing integration of LTE-WLAN at the RAN level is based on dual-connection options, i.e., 2C and 3C, as defined by 3GPP LTE Release 12.
The options 2C and 3C illustrated in FIGS. 1 and 2 contain two logical nodes: main base station (MeNB) and WLN logical node. The MeNB refers to a base station that supports the integration and interoperability of LTE-WLN and is responsible for maintaining the RRM (Radio Resource Management) measurement configuration of user equipment and requesting the WLN to provide additional resources for the user equipment based on the received measurement report or traffic status or bearer type, etc. The WLN provides a data transmission service for the user equipment or rejects the request due to insufficient resources after receiving the request from the MeNB. The WLN refers to a logical node having functions of receiving user data from the MeNB and forwarding the data to the user equipment by using the radio resources provided by the WLAN.
The option 2C illustrated in FIG. 1 has the following characteristics: (1) the MeNB communicates with a service gateway through an S1-U interface; (2) a data radio bearer (DRB) is not split in the MeNB; (3) a Packet Data Convergence Protocol (PDCP) entity at the MeNB encapsulates the PDCP SDU from the service gateway into a format required by a receiving entity (known as an adaptation entity or WLN entity) of the WLN and sends it to the adaptation entity. The adaptation entity encapsulates the data received from the PDCP entity of the MeNB as required and then transmits it to the user equipment (UE) via the WLAN radio resources. Herein, the UE may be a user terminal, a user node, a mobile terminal, or a tablet computer. In the following description, the data radio bearer with characteristics of the option 2C is referred to as a WLN non-split data radio bearer (WLN non-split DRB).
The option 3C illustrated in FIG. 2 has the following characteristics: (1) the MeNB communicates with a service gateway through an S1-U interface; (2) a data radio bearer is split in the MeNB; (3) for a split data radio bearer, there is a corresponding radio link control (RLC) entity in the MeNB. The PDCP entity located at the MeNB encapsulates the PDCP SDU from the service gateway into a PDCP PDU and sends a portion of the encapsulated PDCP PDU to the UE through the RLC entity, the MAC entity, and the physical layer of the MeNB. The remaining PDCP PDU is further encapsulated as required and sent to the adaptation entity of the WLN and to the UE via radio resources provided by the WLAN. In the following description of the present invention, a data radio bearer having the characteristics of the option 3C is referred to as WLN split data radio bearer (WLN split DRB).
The master cell group (MCG) cited in the present invention refers to a group of serving cells of UE, and the group of serving cells contains a primary cell (PCell) and 0 or more secondary cells (SCell). Based on the architecture of options 2C and 3C, in a system of LTE-WLAN integration and interoperation, in a case where user data transmitted by a DRB is transmitted only by using the MCG (i.e., the user data transmitted by a DRB is transmitted to UE via the PDCP entity, the RLC Entity, MAC entity, and physical layer (PHY) of the MCG), then the DRB is called the master cell group DRB (MCG DRB). In a case where the user data transmitted by a DRB is transmitted simultaneously using the radio resources of the MCG and the radio resources of the WLAN (i.e., a part of the user data transmitted by a DRB is transmitted to UE via the PDCP entity, the RLC entity, the MAC entity, and the physical layer PHY of the MCG, and the other part of the user data is transmitted to the UE via the PDCP entity of the MCG and the WLAN), then the DRB is called WLN split DRB (WLN split DRB). In a case where the user data transmitted by a DRB is encapsulated by the PDCP entity of the a MCG and transmitted by using the radio resources provided by the WLAN, this DRB is called a WLN non-split data DRB (WLN non-split DRB). In other words, the user data of the WLN non-split DRB is not transmitted by the radio resources provided by the LTE, but rather is encapsulated by using the PDCP entity of the MCG, sent to the WLN, and then transmitted to the user equipment through the WLAN radio resources. In the present invention, the WLN split DRB and the WLN non-split DRB are collectively referred to as WLN DRB. That is, the WLN DRB mentioned in the present invention may indicate either a WLN split DRB or a WLN non-split DRB.
In a LTE-WLAN integrated system, it is necessary to dynamically perform DRB reconfiguration between the MeNB and the WLN, based on the available radio resources of the MeNB and the WLN. For example, when the MeNB cannot provide sufficient radio resources for the UE, the WLN may be requested to provide radio resources for the UE, i.e., the MCG DRB is reconfigured as a WLN split DRB or WLN non-split DRB. When the MeNB and the WLN are simultaneously serving the UE (i.e., based on the architecture of the option 3C), in a case where the MeNB has more radio resources available to the UE for a period of time, but the WLN does not have sufficient radio resources available to the UE, the MeNB may reconfigure the DRB to the MeNB. In other words, reconfiguring the WLN split DRB as an MCG DRB, and in a case where the MeNB has no radio resources available to the UE for a period of time, but the WLN can provide more radio resources for the UE, the MeNB may reconfigure the DRB to the WLN, that is, the WLN split DRB is reconfigured as a WLN non-split DRB. When the WLN provides radio resources for UE alone to carry out data transmission after the data is encapsulated by the PDCP entity of the MeNB (i.e., an architecture based on the option 2C), in a case where the MeNB has more radio resources available to the UE for a period of time or the WLN does not have sufficient radio resources available to the UE, the MeNB may reconfigure the DRB to the MeNB. In other words, reconfiguring the WLN split DRB as an MCG DRB, and in a case where the MeNB can provide a portion of radio resources for the UE for a period of time, in this case, the WLN non-split DRB is reconfigured as a WLN split DRB.